Three rules:
Negotiate 30 to 50 percent on opening rates where realistic. Brands achieve on average 37 percent cost reduction through negotiation; beyond that range, the gap rarely closes
Maximum 1 to 2 counter offers. If the gap will not close, move on, or negotiate down the number of posts or usage rights instead
Briefs are binding. The brief is the contract: everything you want must be in it before the campaign goes live. You cannot request things outside the brief during feedback